The goal of the Phase II program is the development of a prototype, battery-operated wearable air supply for pneumatically-operated implanted artificial hearts to readiness for productization and clinical evaluation. The ultra-miniaturized air supply is designed to be worn by ambulatory patients with implanted pneumatic total artificial hearts or implanted, pneumatic left-ventricular assist devices. The wearable supply will permit mobility in the home, and away from home it will provide necessary reliability and back-up to larger, heavier portable units. The device has major short-term utility as a supply for pneumatic artificial heart implants in patient awaiting heart transplants. A novel design for a wearable air supply, developed during Phase I, consists of a rotary compressor, driven by a brushless DC motor to supply air to the ventricle through an electromagnetically- actuated directional valve, all controlled by a micro-computer. An experimental unit has successfully driven a single Utah pneumatic ventricle on a Mock Circulation. A two-year program for Phase II is planned. Year 1 will be devoted to component development and test and construction and in-vitro tests of engineering prototypes. During the second year endurance tests, in-vitro tests and in-vivo tests in calves will be made.